func (cnf *ZkConfig) DataDir() string {
	baseDir := env.VtDataRoot()
	if cnf.Global {
		return fmt.Sprintf("%v/zk_global_%03d", baseDir, cnf.ServerId)
	}
	return fmt.Sprintf("%v/zk_%03d", baseDir, cnf.ServerId)
}

// HttpHandleSnapshots handles the serving of files from the local tablet
func HttpHandleSnapshots(mycnf *mysqlctl.Mycnf, uid uint32) {
	// make a list of paths we can serve HTTP traffic from.
	// we don't resolve them here to real paths, as they might not exits yet
	snapshotDir := mysqlctl.SnapshotDir(uid)
	allowedPaths := []string{
		path.Join(vtenv.VtDataRoot(), "data"),
		mysqlctl.TabletDir(uid),
		mysqlctl.SnapshotDir(uid),
		mycnf.DataDir,
		mycnf.InnodbDataHomeDir,
		mycnf.InnodbLogGroupHomeDir,
	}

	// NOTE: trailing slash in pattern means we handle all paths with this prefix
	http.Handle(mysqlctl.SnapshotURLPath+"/", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		handleSnapshot(w, r, snapshotDir, allowedPaths)
	}))

}

// createTopDir creates a top level directory under TabletDir.
// However, if a directory of the same name already exists under
// vtenv.VtDataRoot(), it creates a directory named after the tablet
// id under that directory, and then creates a symlink under TabletDir
// that points to the newly created directory.  For example, if
// /vt/data is present, it will create the following structure:
// /vt/data/vt_xxxx /vt/vt_xxxx/data -> /vt/data/vt_xxxx
func (mysqld *Mysqld) createTopDir(dir string) error {
	vtname := path.Base(mysqld.TabletDir)
	target := path.Join(vtenv.VtDataRoot(), dir)
	_, err := os.Lstat(target)
	if err != nil {
		if os.IsNotExist(err) {
			topdir := path.Join(mysqld.TabletDir, dir)
			log.Infof("creating directory %s", topdir)
			return os.MkdirAll(topdir, os.ModePerm)
		}
		return err
	}
	linkto := path.Join(target, vtname)
	source := path.Join(mysqld.TabletDir, dir)
	log.Infof("creating directory %s", linkto)
	err = os.MkdirAll(linkto, os.ModePerm)
	if err != nil {
		return err
	}
	log.Infof("creating symlink %s -> %s", source, linkto)
	return os.Symlink(linkto, source)
}

func SnapshotDir(uid uint32) string {
	return fmt.Sprintf("%s/%s/vt_%010d", env.VtDataRoot(), snapshotDir, uid)
}

func TabletDir(uid uint32) string {
	return fmt.Sprintf("%s/vt_%010d", env.VtDataRoot(), uid)
}

func main() {
	dbConfigsFile, dbCredentialsFile := dbconfigs.RegisterCommonFlags()
	flag.Parse()

	if err := servenv.Init("vttablet"); err != nil {
		relog.Fatal("Error in servenv.Init: %s", err)
	}

	tabletAlias := tabletParamToTabletAlias(*tabletPath)

	mycnf := readMycnf(tabletAlias.Uid)
	dbcfgs, err := dbconfigs.Init(mycnf.SocketFile, *dbConfigsFile, *dbCredentialsFile)
	if err != nil {
		relog.Warning("%s", err)
	}
	dbcfgs.App.Memcache = *rowcache

	if err := jscfg.ReadJson(*overridesFile, &schemaOverrides); err != nil {
		relog.Warning("%s", err)
	} else {
		data, _ := json.MarshalIndent(schemaOverrides, "", "  ")
		relog.Info("schemaOverrides: %s\n", data)
	}

	initQueryService(dbcfgs)
	initUpdateStreamService(mycnf)
	ts.RegisterCacheInvalidator()                                                   // depends on both query and updateStream
	err = initAgent(tabletAlias, dbcfgs, mycnf, *dbConfigsFile, *dbCredentialsFile) // depends on both query and updateStream
	if err != nil {
		relog.Fatal("%s", err)
	}

	rpc.HandleHTTP()

	// NOTE(szopa): Changing credentials requires a server
	// restart.
	if *authConfig != "" {
		if err := auth.LoadCredentials(*authConfig); err != nil {
			relog.Error("could not load authentication credentials, not starting rpc servers: %v", err)
		}
		serveAuthRPC()
	}

	serveRPC()

	// make a list of paths we can serve HTTP traffic from.
	// we don't resolve them here to real paths, as they might not exits yet
	snapshotDir := mysqlctl.SnapshotDir(tabletAlias.Uid)
	allowedPaths := []string{
		path.Join(vtenv.VtDataRoot(), "data"),
		mysqlctl.TabletDir(tabletAlias.Uid),
		snapshotDir,
		mycnf.DataDir,
		mycnf.InnodbDataHomeDir,
		mycnf.InnodbLogGroupHomeDir,
	}

	// NOTE: trailing slash in pattern means we handle all paths with this prefix
	http.Handle(mysqlctl.SnapshotURLPath+"/", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		handleSnapshot(w, r, snapshotDir, allowedPaths)
	}))

	// we delegate out startup to the micromanagement server so these actions
	// will occur after we have obtained our socket.
	umgmt.SetLameDuckPeriod(float32(*lameDuckPeriod))
	umgmt.SetRebindDelay(float32(*rebindDelay))
	umgmt.AddStartupCallback(func() {
		umgmt.StartHttpServer(fmt.Sprintf(":%v", *port))
		if *securePort != 0 {
			relog.Info("listening on secure port %v", *securePort)
			umgmt.StartHttpsServer(fmt.Sprintf(":%v", *securePort), *cert, *key, *caCert)
		}
	})
	umgmt.AddStartupCallback(func() {
		c := make(chan os.Signal, 1)
		signal.Notify(c, syscall.SIGTERM)
		go func() {
			for sig := range c {
				umgmt.SigTermHandler(sig)
			}
		}()
	})

	relog.Info("started vttablet %v", *port)
	umgmtSocket := fmt.Sprintf("/tmp/vttablet-%08x-umgmt.sock", *port)
	if umgmtErr := umgmt.ListenAndServe(umgmtSocket); umgmtErr != nil {
		relog.Error("umgmt.ListenAndServe err: %v", umgmtErr)
	}
	relog.Info("done")
}